In the field of magnetic heads to be mounted on a magnetic recording apparatus such as a hard disk drive (HDD), recently, the recording method is being shifted from longitudinal recording to perpendicular recording in order to improve the recording density with respect to a magnetic recording medium such as a hard disk. The perpendicular recording method achieves high linear recording density and also has an advantage that the recording medium after recording becomes highly resistant to heat fluctuation.
A perpendicular recording magnetic head is provided with a coil film for generating a magnetic flux and a main magnetic pole film for guiding the magnetic flux to a recording medium. The main magnetic pole film has such a pattern that its magnetic pole tip for supplying a perpendicular magnetic field to a magnetic recording medium is a tapered small width portion and a large width portion (or yoke portion), which functions as a magnetic flux supplying portion to the small width portion, is disposed in continuous relation with the rear end of the small width portion. The main magnetic pole film is generally formed on an electrode film, which functions as a seed film, by electroplating.
In order to improve the recording capacity of a hard disk drive (HDD), meanwhile, the recording resolution must be improved by increasing the coercive force of the magnetic recording medium while increasing the track density by reducing the width of the magnetic pole tip formed by the small width portion of the main magnetic pole film in the magnetic head.
In order to ensure sufficient overwrite characteristic (OW) for the magnetic recording medium of such a high coercive force, the main magnetic pole film of the magnetic head must have a high saturation magnetic flux density. Heretofore, accordingly, a high saturation magnetic flux density material, for example, a high saturation magnetic flux density magnetic material such as a FeCo-type material, a CoNiFe ternary alloy film, FeC or FeN, has been used for the plated film of the main magnetic pole film, and the electrode film, which functions as a seed film therefor, has also been made of a high saturation magnetic flux density magnetic material. For example, Japanese Unexamined Patent Application Publication No. 2006-253252 discloses a main magnetic pole in which a FeCoNi plated film is formed on a FeCoNi electrode film.
On the other hand, Japanese Unexamined Patent Application Publication No. 2006-269690 discloses a main magnetic pole film in which a FeCo alloy plated film is formed on a non-magnetic conductive layer and then used as an electrode film for formation of a FeNi alloy plated film thereon.
Another important factor which has to be kept in mind with respect to perpendicular recording magnetic heads is the problem of pole erase that a signal recorded on the magnetic recording medium becomes erased by the main magnetic pole film when recording is not performed.
In the perpendicular recording magnetic heads, the main magnetic pole film for recording has its hard axis directed along an air bearing surface direction to perform recording in a magnetization rotation mode. That is, residual magnetization along the air bearing surface direction is minimized to prevent an excess magnetic flux from being generated when recording is not performed, thereby avoiding the pole erase. In order to assure this function, the coercive force Hch of the main magnetic pole film along the hard axis has to be kept low. In the present situation where the width at the tip of the main magnetic pole film (or track direction width) has been decreasing greatly according to the demand for high density recording, moreover, the magnetic domain cannot be arranged orderly at the tip, and therefore it is also important to keep low the coercive force Hce along the easy axis.
As described above, the main magnetic pole film of the perpendicular magnetic recording element has such a pattern that the small width portion for supplying a perpendicular magnetic field to a magnetic recording medium is continuous with the large width portion for supplying a magnetic flux to the small width portion. Since the small width portion and the large width portion have different roles, as set forth above, it is desirable to give them appropriate different magnetic properties.
However, as disclosed in Japanese Unexamined Patent Application Publication Nos. 2006-253252 & 2006-269690, since it has been conventional to grow the plated film on a common electrode film at one stroke as a main magnetic pole film, not only the overwrite characteristic at the small width portion and the large width portion but also the coercive force has been primarily determined by magnetic properties of the electrode film and the plated film, and therefore it has been impossible to reconcile them.
In addition, since high saturation magnetic flux density magnetic materials are generally of a high coercive force, too, the improvement in overwrite characteristic by increasing the saturation magnetic flux density cannot be reconciled with the improvement in pole erase by decreasing the coercive force, sacrificing one to improve the other.